• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.862-867
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• 2000

The auxiliary engine exhaust noise in ships are directly transmitted to bridge wing with the only distance attenuation. It is not so practical that no special treatment can be applied between exhaust pipe and bridge wing in order to reduce the transmission of the exhaust noise. In general, a silencer is fitted to reduce the exhaust noise and also noise of bridge wing. The silencer should be properly designed under the consideration of the frequency component of the exhaust noise and the required insertion loss. In this paper, the frequency component of exhaust noise of various engines are compared and a design and a design and installation of silencer to reduce low frequency is introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1033-1037
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• 2007

The final purpose of this study is to develop noise abatement procedures for minimizing the environmental impacts caused by aircraft noise in the vicinity of Gimpo Int'l Airport, and to establish appropriate noise limits and monitoring system. The results of study was suggests for more detail the crucial factors which one is reference noise level, $L_{MAX}=88dB(A)$ at 6.5km after take-off, and second one is to installation the additional three(3) noise monitoring system on both side of runway.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.874-880
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• 2007

The final purpose of this study is to develop noise abatement procedures for minimizing the environmental impacts caused by aircraft noise in the vicinity of Gimpo Int'l Airport, and to establish appropriate noise limits and monitoring system. The results of study was suggests for more detail the crucial factors which one is reference noise level, $L_{MAX}=88 dB(A)$ at 6.5 km after take-off, and second one is to installation the additional three(3) noise monitoring system on both side of runway.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.452-459
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• 1997

For computer aided design and construction of low noisy power plants, indoor and outdoor noise prediction program has been developed. The program utilizes the predefined data of noise sources and building materials and has the faculty to estimate the source level using the empirical formula in case of the measured data not being available. In the noise prediction, the mutual noise propagation between indoor and outdoor sites are considered. The outdoor noise source in the calculation of geometric divergence effects is modelled as the omni-directional finite line or planar source according to the source geometry and the receiving points. Outdoor noise prediction is carried out to consider the diffraction effect due to plant structures as well as the attenuation effect due to atmospheric absorption and soft ground. The results of indoor and outdoor noise prediction for a recently constructed diesel engine power plant show good agreement with the measured.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.57-65
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• 2017

This paper presented a method of designing low-power feedback active noise control filter optimized for headphones/earphones. Using constrained optimization, we obtained a high order FIR noise control filter to ensure reasonable noise attenuation performance at high sampling frequency environment. Then using infinite impulse response (IIR) approximation method called Balanced Model Truncation (BMT), we obtained a low order IIR noise control filter suitable for low-power digital signal processing system like headphones/earphones. For further performance improvement, we utilized frequency warping method so that we could obtain more accurately approximated IIR filter and we ensured system stability by reconstructing the low order IIR filter in form of cascaded second order IIR filters. ANC simulation with white noise and stability test verified that the proposed algorithm had superior attenuation performance and better robustness compared to the conventional algorithm.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.3 no.1
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• pp.20-26
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• 2000

In order to propose the design and installation information of vegetation belt, field investigation were carried out in the noise pollution control facilities of highway and the streets of a city for two years(1998~1999), and field tests were performed to analyze the noise attenuation effect of them. The noise pollution control facilities were generally classified into three types (noise barrier and vegetation belt type, mounding and vegetation belt type, vegetation belt type only). Most soundproof facilities were proved the noise reduction effects. But according to width, height, structure, auditory distance and planting forms of them, difference of noise reduction effects were investigated. The soundproof facility was suitable the mounding and vegetation belt type in the consideration of road environment, and the installation standard of vegetation was estimated that the width of vegetation was at least 20m and the length of that was 2 times in the distance from noise source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1344-1349
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• 2000

With rapidly industrial development, a railway has become of a main traffic means. But, the railway noise has caused much annoyance for the residents living nearby railway tracks. Therefore, in our country, for established of Quite dwelling environment, execute regulation standard of railway noise from January 1, 2000. Efficiency soundproofing measures, however, are very difficult because of the lack of basic data and insufficiency of the existing research. In this point, this study attempts to survey the characteristics of attenuation and propagation of railway noise in by existence of noise barrier. And this study intends to get the basic data for establishment of a standard about railway noise.

• Journal of KSNVE
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• v.7 no.6
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• pp.909-918
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• 1997

Combustion oriented noise is a part of engine noise, which is mainly determined by the in-cylinder pressure profile and the structure attenuation of an engine. A numerical model for predicting the in-cylinder pressure profile and the resultant combustion noise developed by the use of a commercial code. The model is experimentally validated and updated based on the performance as well as the noise by considering the fuel injection timing, the fuel injection rate, Cetane number, intake temperature, and compression ratio. For providing a design guide of a fuel injector for a low combustion noise engine model, the optimal parameters of injection pressure profile, injection rate profile, and injection timing are determined, which gives the 5 dBA noise reduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.731-736
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• 2004

The exhaust noise of auxiliary engine in ships is directly transmitted to bridge wing with only distance attenuation. It is not easy to find out practical treatment to be applied between exhaust pipe and bridge wing to reduce the transmission of the exhaust noise. In general, therefore, a silencer is fitted to reduce the exhaust noise and correspondingly noise of bridge wing. The silencer should be properly designed under the consideration of the frequency component of the exhaust noise and the required performance such as noise reduction or insertion loss. In general, the gas inside the exhaust pipe flows with high temperature and speed and thus onboard test condition is more adverse than the standard atmospheric condition. In this study, the test method to evaluate silencer performance using a probe microphone is introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1162-1168
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• 2007

In many fire emergencies, the audible fire alarm signals are very important to save the occupant's life. But as the sound insulation of building elements has been improved, it is more difficult for occupant to recognize the fire alarm signals when the fire alarm worked. This is the study to show the sound attenuation of the fire alarm sounder system in apartment buildings. We measured and analyzed the sound attenuation level in 17 units, and the results were compared with the minimum sound level at sleeping area by NFPA(National Fire Protection Association) 72. When only the fire alarm worked in stair hall, the sound levels in bedroom were in the range of $30.6{\sim}42.8dB(A)$ and the differences between sound level and ambient sound level in bedrooms were in the range of $7.1{\sim}13.8dB(A)$. And when the emergency broadcasting device in the livingroom and the fire alarm worked simultaneously, the sound levels in bedrooms were in the range of $54.2{\sim}63.0dBA$. Finally, it was showed that the fire alarm sounder system didn't give a sufficient sound level in bedroom to awake out of sleep.